Christmas Light/Switchbox Wiring

[jamekelburg]

I have a school project and part of the requirement is to build a circuit that uses light and simple parallel and series wiring to show weight progression. The weight progression being shown is weight being added to a balsa wood tower. What I'm planning on doing is building a box with 8 bars cut in it where I will attach christmas lights in the slots in between. I'm thinking about using about 100 christmas lights. I found they run brightly on about 1.1 volts. I think I'm going to have 12 lights per bar. To turn these bars on and off I have 8 switches so I'll have a separate box in which the switches would be held. I'm wondering how I would go about powering each bar. I know I have to step down the power but I'm unsure about how to go about this. Someone told me a single PC power supply would work. I have a lot of simple electronics supplies like transformers and resistors. Oh and capacitors but I don't know how useful those are. Any suggestions? I'm in America so my outlet is 110v.

 

[dlgoff]

Welcome to PF jamekelburg.

You need to know how much current your LEDs draw at 1.1 volts.

http://en.wikipedia.org/wiki/LED_circuit"

My advice would be to purchase "wall wort/s" that are UL approved for the project.

 

[jamekelburg]

Thank you for the timely response. Sorry but I didn't specify that they are mini incandescent bulbs, not LEDs. They came on a string of 100 and my wall outlet is 110v so I figured each bulb is 1.1v because I divided the power by the number of bulbs. I heard those circuits are easier to configure.

 

[dlgoff]

Considering what you have, I would still consider using some UL listed power source unless you have experience with mains power.

There is a safety issue.

 

[jamekelburg]

okay so would a PC power supply work? and if not could you post an alternative?

 

[dlgoff]

Do you know how many watts your string of 100 bulbs requires? I'm not sure that a PC supply would have enough power available. Do you know how much the PC supply is rated for from the 12 volt output?

 

[jamekelburg]

I honestly have no idea. I'm not too great with electricity. Here's what the plug says:
120v 0.2A 60Hz 2.5v bulbs

 

[dlgoff]

That would mean the power required would be P=IV=(0.2amp)x(120volts)=24 watts.

I don't know what power your PC supply can provide (the 12 volt dc supply line). 24 watts doesn't sound like too much. You could check-out/(experiment) with a [STRIKE]string of 8[/STRIKE] string of 12 (in series) on the 12volt output and see if they are bright enough.

 

[jamekelburg]

Okay thanks. Final thing, but will the parallel or series wiring of the lights affect it because I'm going to have to have half series and half parallel.

 

[dlgoff]

That would mean the power required would be P=IV=(0.2amp)x(120volts)=24 watts.

I don't know what power your PC supply can provide (the 12 volt dc supply line). 24 watts doesn't sound like too much. You could check-out/(experiment) with a string of 8 on the 12volt output and see if they are bright enough.

This (bold) should have read a string of 12.

Okay thanks. Final thing, but will the parallel or series wiring of the lights affect it because I'm going to have to have half series and half parallel.

If one string of 12 (in series) works without overheating your 12 volt PC supply, then try another string of 12 (in series) in parallel with the first string.

So yes. Parallel each of the 8 sets of 12 bulbs. I hope your supply can handle it. Give it a try.